Item: The Iran letter from 47 Republican senators is the latest evidence demonstrating “just how badly congressional Republicans have messed up on foreign policy,” as international relations scholar Dan Drezner put it in The Washington Post.

Item: Senate Republicans are still struggling to find the votes to confirm Loretta Lynch, the attorney general nominee.

Item: Senate Republicans may have spiked a bill against human trafficking by adding an abortion provision, turning a consensus measure into a partisan fight that they don’t have the votes to win (in the Senate, or over a presidential veto). Moreover, by slipping in the provision without notifying Democrats, they may have jeopardized any hope of Senate comity in the near future.

All of that has happened in the week or so since the Homeland Security funding bill fiasco. So much for the idea that the Mitch McConnell Senate would be a chamber that worked.

The GOP would rather pose as an aggrieved, oppressed minority even when it controls Congress.

What explains these disasters? Republicans continue to make decisions driven by their fears of facing primary challenges from candidates who claim to be more conservative than they are.

Take, for example, the Lynch nomination. Attorney General Eric Holder will stay on until a successor is confirmed, so the choice is really Lynch or Holder — and almost every Republican would prefer Lynch.

Republicans continue to make decisions driven by their fears of facing primary challenges from candidates who claim to be more conservative than they are.

The problem is that Lynch, like any possible attorney general nominee selected by Barack Obama, will eventually side with the president on an issue that fires up conservative talk shows and websites. She has already indicated she believes the president’s executive actions on immigration are legal. As a result, any Republican who votes for her may be handing a campaign issue to a potential opponent.

Similarly, most Republicans found it far easier to sign a yahoo letter to Iran from a brand-new senator than to have to explain why they weren’t on board with whatever position other conservatives supported. And given that the abortion measure has been added to the human-trafficking bill, they can’t back the legislation without it. Republicans are more scared of being called supporters of abortion in a primary than they are of being called supporters of human trafficking in a general election.

Many Republicans — maybe most of them — care more about proclaiming their devotion to conservative ideology than they do about scoring victories on specific policies. So signing the Iran letter wasn’t about producing the most conservative results. It was about affirming True Conservative loyalty.

In practice, this means the Republican Party (along with its attached lucrative conservative marketplace) has few incentives for governing. It would rather pose as an aggrieved, oppressed minority even when it controls Congress. The conservatives who start battles are likely to be rewarded no matter how badly things turn out.

Thus, the multiple fiascos we’ve seen in the last two months aren’t flukes. Expect more where they came from.